Machines for cutting grooves in a cured pavement such as concrete, asphalt or the like are well known. Such machines conventionally weigh 400 pounds or more. See for example, U.S. Pat. No. 4,456,303. Because of the heavy weight and large size, such machines must be used by a skilled operator who can control and guide them to perform the desired cutting operation. Such machines are constructed so that the cutting blade is off center. This facilitates the use of the blade for cutting close to buildings or other solid structures such as curbs or the like. While this is a useful feature, the placement of the blade off-center creates a weight imbalance which makes it difficult for even a skilled operator to cut a straight groove in pavement. These saws are only useful in cutting grooves in pavements which have fully cured and are not useful in grooving expansion joints in uncured or "green" concrete because of their weight. The use of the large and heavy pavement saws on green concrete will leave impressions in the concrete and thereby permanently ruin the surface.
Thus there was a need for a saw which cuts a groove in green concrete. One such saw that is currently on the market is the Soffcut saw manufactured by Soffcut International. This saw is little more than a circular saw mounted on a skateboard-type plate. It is light in weight, on the order of about 25 lbs. However, due to its light weight its performance suffers. It pulls apart the green concrete aggregate rather than cutting it, leaving voids and an uneven cut. The voids result in a weakened pavement after curing which is subject to cracking. Another such saw is the Green Machine.RTM. manufactured by Cardinal Industries. U.S. Pat. No. 5,086,750 discloses still another green concrete cutting saw. These green concrete cutting machines have not been entirely satisfactory for various reasons. The blades cut in an upward direction which often pulls aggregate out of green concrete or loosens it sufficiently to weaken the concrete. Also, the machines have off-center blades, use hard skateboard-type wheels which can leave marks in some green concrete, and are difficult to steer and maintain a straight line cut. Moreover, such saws, because of their light weight, are incapable of cutting cured concrete or other cured pavement. When used for cutting green concrete they are preferably best used at an early stage of curing since concrete that is almost fully cured may force the saw blade to lump up out of the cutting groove leaving a groove of uneven depth. In addition, such saws can only cut to a maximum depth of about 1.25" (3.2 cm), thereby restricting their use to concrete slabs less than about 5" (12.7 cm) thick.
Accordingly, there is a need for a saw which can cut uncured pavement, particularly green concrete, and cured pavement equally well and without the need for significant operator control. Preferably, such a saw should be capable of cutting a straight groove with little or no operator assistance. When used with green concrete, the saw must not leave any visually noticeable markings on the green concrete and be capable of cutting deep grooves at a depth of up to about 3.5" (8.9 cm) so that it can be used on green concrete slabs up to 14" (35.6 cm) thick.